1. Field of the Invention
The present invention relates to the field of digital computation and more particularly to the recursive processing of a time series of digital data. Digital filtering is one important category of recursive processing.
2. Description of the Prior Art
Recursive digital filters are well known. In general they involve multiplication and addition operations on numerical sequences in order to produce new numerical sequences. In such recursive filters, the output sequence is fed back and combined and the input sequence. The values of the terms of the sequence are necessarily quantized to a fixed number of bits, and thus as part of the filtering operation it is necessary to round or truncate in order to make the number of bits at the output equal to the number of bits at the input. This rounding or truncation introduces an error (noise) into the filter. This error is random in nature. Of particular concern is the bias (DC) portion of the error, which is troublesome in recursive low pass filters. In such filters any bias error is fed back to the input and tends to magnify the error because of error integration.